When it comes to home automation, the prevailing wireless protocols over the last few years have been Z-Wave, ZigBee (including closed implementations such as Crestron’s Infinet), Insteon, proprietary technologies such as Lutron’s ClearConnect, and super-efficient narrowband technologies in the 300 to 400 MHz range, used most often in the security industry (for example, Honeywell’s 5800 Series sensors at 345 MHz).
Higher-bandwidth Bluetooth and Wi-Fi have rarely been viewed as “home automation standards.” But that is changing.
Low-power variations of these two ubiquitous standards are making them more believable as home-control standards in the not-too-distant future.
As a close cousin of Wi-Fi, 6LoWPAN (IPv6 over Low power Wireless Personal Area Networks) enables IP packets to be delivered over 802.15.4 radios – the same radios used for ZigBee – allowing even small, lightweight devices to have their own IP addresses.
Leading the charge for 6LoWPAN in the home automation category is Greenwave Reality (with 6LoWPAN technology developer NXP), which embeds the technology in its light switches, gateways, energy monitors and other smart devices. The products have found their way into a substantial number of Scandinavian homes thanks to utility initiatives in Sweden and Denmark.
Likewise, the Bluetooth spinoff Bluetooth Low Energy (BLE), also known as Bluetooth Smart, offers an appealing platform for home-control applications.
By sending small bursts of data instead of continuous streams, BLE consumes just a small fraction of the energy required for full-blown Bluetooth, making the technology acceptable for battery-operated devices such as smart watches and proximity sensors.
Apple was the first major operating system to support BLE in 2012 and now the company is using the platform for its new iBeacon messaging devices for retail environments. Batteries for the devices could last up to three years. All of the major OS developers have followed suit, meaning virtually every smart device supports or will support the format, which is a feature of Bluetooth 4.0.
That being the case, hundreds of Bluetooth Smart devices are now on the market – from Nike+ smart shoes to numerous wearable telehealth products, light bulbs and door locks that can be controlled directly from an app without the need for gateways or onerous network configurations.
The Case of Single-Purpose Devices
Many of the leading research firms covering the connected home insist Bluetooth LE will be the standout technology for wireless sensor networks (WSN) in the next few years, surpassing ZigBee and others.
ON World predicts BLE will be the fastest growing WSN technology over the next five years. ABI Research concurs, estimating shipments of BLE-enabled products at over 133 million units by 2018, and asserting the platform will surpass ZigBee’s market share in home automation by 2015.
Even without that volume, complete Bluetooth modules today cost only about $2.50 in volume, according to sources in the smart-home space. That compares to about $4 or $5 for equivalent ZigBee or Z-Wave solutions.
Neither Wi-Fi nor Bluetooth is “optimized for what ZigBee and Z-Wave are optimized to do,” says industry veteran Bill Rose of WJR Consulting. “But in reality, just looking back over history, cheap is good.”
To be sure, ZigBee and Z-Wave today are the best bets (off-the-shelf) for home automation, given their mesh-networking architectures, low power requirements, self-healing features, simplicity of device-enrollment, interoperability (in most cases) across a broad ecosystem of products, and most importantly vast libraries of smart-device profiles.
“When thousands or tens of thousands of devices may be in a single network, the devices must autonomously perform tasks such as assigning network addresses and selecting the best, most efficient communication paths,” says a spokesperson for the ZigBee Alliance. “Networks must be reliable and tolerate faults including dealing with interference and/or the failure of individual devices. Of course, the devices must be low-cost and low-power so they are affordable to install and operate. ZigBee was conceived and developed to deliver standards-based sensor and control networks, and is optimized to meet these requirements and work reliably in precisely such environments and applications.”
That is not to say, of course, that Wi-Fi and Bluetooth groups won’t create their own device profiles for interactivity or implement other features inherent in ZigBee and Z-Wave technologies. In any case, interoperability across multiple vendors has lost some luster over the years with the popularity of single-purpose apps.
“When I look at a typical home today and how smart products roll out,” says Rose, “people buy one or two devices at a time, usually not a complete system.”
In such scenarios, he adds, “they probably just want to connect to a wireless access point, which may be located at the other end of the house.”
This concept is not lost on product developers, many of which have developed smart devices with complete Wi-Fi stacks – Belkin Wemo, Nest thermostats, Fitbit Smart Scales, and several varieties of door locks, to name a few.
Rose says, “There’s no question in my mind, if I were to develop a smart thermostat today, I would use Wi-Fi. No matter where it is situated in the house it will reach the access point, and it likely will have a low-voltage power source nearby. If my interest is in selling thermostats – and I don’t have to sell you a gateway – that is the best solution.”
As for Bluetooth, distance appears to be a limiting factor for whole-house control, but there is talk of a mesh-type solution and some developers are launching Bluetooth extenders – like the AIRcable BLE Gateway from Wireless Cables Inc., which can extend a signal “halfway into the street,” says principal Juergen Kiehnhoefer.
But, as with Z-Wave and ZigBee, a BLE mesh network means little if there are not multiple nodes on the network.
ZigBee, Z-Wave Strongest for Whole-House Integration
Bottom line: “Wireless technology has to be matched to the application,” says Fred Bargetzi, vice president technology for leading home automation developer Crestron, which makes scores of wireless devices based on its own version of ZigBee. “The technology applied to entire systems is often different than the technology applied to single devices. To say that ‘Wi-Fi will win out over other technologies’ would really be shortsighted. For example, making a battery-powered sensor to last for 10 years using Wi-Fi would be quite a challenge based on the power requirements of that technology.”
He notes that the IEEE is working on a new low-power Wi-Fi standard (802.11ah) to compete with ZigBee and Z-Wave “but this will work in a different band (900 MHz) which negates the benefit of using your existing Wi-Fi network.”
From the Z-Wave camp, industry veteran Avi Rosenthal of Linear LLC says that while BLE is attractive for single-purpose devices today, “it is hard to imagine dozens of devices all trying to compete with the hub at the same time.”
In the case of Bluetooth and Wi-Fi, multiple devices can bog down or confuse the network. Conversely, “as the number of connected devices grows, the scalability of a Z-Wave mesh network only gets stronger,” Rosenthal says.
While most of the established home-control companies are clinging to the lower-rate protocols, at least a couple are migrating to Wi-Fi. When TiO emerged from Colorado vNet last year, for example, the new company abandoned ZigBee for Wi-Fi for lighting controls and thermostats.
And when Savant Systems launched its new line of wireless dimmers and keypads last year, it too chose Wi-Fi, adding a microUSB port on the devices for configuration at the switch location.
“That’s always been a problem with Wi-Fi,” says Tim McInerney, director of product marketing for Savant. “We have eliminated that problem with our solution.”